1. Field of the Disclosure
This disclosure relates to an image data processing method and a stereoscopic image display using the same.
2. Discussion of the Related Art
As the stereoscopic image reproduction technology is applied to display devices, such as a television or a monitor, now is the age in which people can view 3D stereoscopic images even at home. A stereoscopic image display may be divided into a glasses type and a non-glasses type. In the glasses type, left and right parallax images each having a different polarization direction are displayed on a direct-view display or projector, and a stereoscopic image is displayed using polarization glasses or liquid crystal shutter glasses. In the non-glasses type, optical parts, such as a parallax barrier and a lenticular lens, are installed in front of a display screen to separate optical axes of left and right parallax images.
Visual factors that allow a person to perceive stereoscopic effects, i.e., depth cues, may include physiological factors and empirical factors. The physiological factors include accommodation, convergence, binocular disparity, etc.
The empirical factors include monocular movement disparity, retinal image size, linear perspective, areal perspective, overlapping, contrast, texture gradient, etc. The empirical factors allow a person to feel a stereoscopic effect with a learned sense of perspective, such as a sense of perspective on the difference in size between objects, a sense of perspective on the overlap between objects, a sense of perspective on the difference in brightness between objects, and a sense of perspective on the difference in sharpness between objects. For example, a human brain, after learning a sense of perspective, perceives the larger object to be nearer when seeing a larger object and a smaller object, perceives a more forward object to be nearer when seeing two objects overlapping, and perceives the bright object to be nearer when seeing a bright object and a dark object at a time. Also, the human brain that has learned perspective perceives the clear object to be nearer when seeing a clear object and an unclear object.
When a viewer views a 3D stereoscopic image reproduced by a stereoscopic image display, the viewer may feel much fatigued or have nausea or headache, mainly due to physiological factors. These symptoms are because the position of the image of an object (or subject) the viewer sees is different from the focal distance.
When the viewer sees a subject, the eyes converge to a point, which is referred to as convergence. The convergence angle θ varies depending on how far the viewer's eyes are from the subject. As shown in FIG. 1, the convergence angle θ is an angle formed between the eyes and the subject when the viewer sees the subject. The farther the distance from the viewer's eyes to the subject, the smaller the convergence angle θ; when the viewer sees a subject at a very far distance, the convergence angle θ is close to 0°.
For an object the viewer perceives through the eyes in an actual situation, the convergence position coincides with the accommodation position, as shown in (a) of FIG. 1. Thus, the distance perceived by convergence and the distance perceived by accommodation are equal. Accordingly, the viewer may feel a stereoscopic effect without a sense of fatigue in an actual situation. In contrast, as shown in (b) of FIG. 1, when a left-eye image and a right-eye image separated by binocular disparity are displayed on a display panel PNL of a stereoscopic image display, the accommodation position is on the screen of the display panel PNL and the image of the object is positioned in front of or behind the screen of the display panel PNL in accordance with 3D input image depth information. As a result, the focal distance L1 of the eyes does not coincide with the distance L2 at which the image of the object is formed. Since the focal distance L1 of the eyes does not coincide with the distance L2 at which the image of the object is formed, the viewer viewing the stereoscopic image display feels fatigued. Especially, the viewer feels more fatigued when viewing a stereoscopic moving image displayed on the stereoscopic image display and when the convergence angle is large, because the difference between the distances L1 and L2 varies for each scene.